Control system for signal seeking receivers



CONTROL SYSTEM FOR SIGNAL SEEKING RECEIVERS Original Filed May '7. 1947 mmvron Dana C026 United States Patent CONTROL SYSTEM FOR SIGNAL SEEKING RECEIVERS Dana W. Cole, Butfalo, N. Y., assignor to Sylvania Electric Products Inc., a corporation of Massachusetts Continuation of abandoned application Serial No. 746,603, May 7, 1947. This application July 24, 1952, Serial No. 300,744

11 Claims. (Cl. 317-149) This invention relates to improvements in signal-seeking receivers, and more particularly .to improvements stabilizing the relay current in signal-seeking receivers.

The present application is a continuation of abandoned application Serial No. 746,603, filed May 7, 1947, entitled Improvements in Signal Seeking Receivers, and assigned to the same assignee as the present application. For the purposes of this disclosure, a signal-seeking receiver, as the term is used herein, means a receiver in which the tuner is driven by some form of power drive, such, for example, as a motor, so that the receiver scans its spectrum until an incoming signal of predetermined strength is tuned in.

When the receiver reaches the frequency of the incoming signal, the scanning action is stopped by the signal itself, and the receiver will remain tuned to the signal which stopped the scanning until the operator closes the switch which starts the scanning again. In the form of receiver with which the present invention is concerned, there is provided a control tube, the plate current of which operates a sensitive relay, which in turn operates a relay in the tuner motor circuit.

Such receiver are particularly useful in automobiles, and when so used, the power for their operation is derived from the car storage battery. Because the voltage available from this battery may fluctuate between five and eight volts, both the A voltage and the B voltage (which is derived from the A voltage through a-vibrator and transformer) will vary in operation.

This variation will ordinarily cause a variation in the plate current of the control tube, which may result in spurious stoppage of the scanning when the storage batterylvoltage is low, and excessive plate current, leading to overheating and possible burn-out of the relay actuating coil, when the storage battery voltage is high.

Itis an object of this invention to provide a system of theclassdescribed, in which the relay hold-in or closing current of the control tube is maintained at or near a constant value for high values of A voltage while increasing it for lowvalues of A voltage (except when the relay is to open in response to incoming signal), regardless of fluctuations of the A battery voltage.

It is a further object of this invention to provide a system of the class described, in which the plate or relay hold-in current does not exceed a predetermined maximumvalue regardless of fluctuations of the storage battery voltage.

It is a further object of this invention to provide a system of the class described, in which only a relatively small number of additional parts, of small cost, are required.

Still other objects and advantages of my invention will be apparent from the specification.

The features of novelty which I believe to be char acteristic of my invention are set forth with particularity in the appended claims. My invention itself, however, both as to its fundamental principles and as to its par- 2,828,451 Patented Mar. 25, 1958 Referring now more particularly to Fig. 1, 1t designates an antenna for collecting incoming signals which are supplied to the radio frequency amplifier, oscillator and converter 11, which includes variable tuned circuits 12 and 13, preferably ganged together for single control, and driven by tuner motor 14 through any suitable drive mechanism.

The output of amplifier, oscillator and converter 11 is supplied to intermediate frequency amplifier 15, thence to detector and audio amplifier 16, and finally to loud speaker or other indicator 17.

Part of the output of intermediate frequency amplifier 15 is supplied to limiter 13 and thence to narrow band selector 19, which may be a crystal bridge circuit having a band pass width of about one-tenth that of the previous circuits. For instance, if intermediate frequency amplifier 15 has a band pass width of 5,000 cycles, narrow band selector 19 will have a band pass width of the order of 500 cycles and will be tuned at or near the center of intermediate frequency amplifier pass band.

The output of the narrow band selector is supplied to terminal 26, thence through condenser 32 to control tube 21. In the form shown, tube 21 is a double triode and may be a 7P8 having a mu of about 50. The tube may comprise a pair of heaters 2111 and 2111 a pair of cathodes 210 and 210 a pair of control electrodes 21g and 21g and a pair of anodes 21:1 and 21:1

Control electrode 21g and anode 21a may be connected together and to one side of condenser 32, and through resistance 22 to the +A terminal of the car storage battery 5% the negative side of which is grounded in this instance. Cathode 210 is connected to ground through resistance 4ll,and the common terminal of resistance 40 and cathode 21c is connected through resistance 41 to the positive side of the B source, the negative side of which is preferably grounded. The B source is a voltage step-up device such, for example, as a vibrator and a rectifier energized from the 'A battery 5!). Accordingly, variations in the output voltage of the A battery 50 cause similar variations in the output voltage of the B source.

Anode 21a, is connected through resistance 23 to control electrode 21g Cathode 210 is connected to ground through self-biasing resistor 24. Anode 21:1 is connected through the energizing coil of relay 25 to +B, and armature 27 is connected to ground and fixed contact 26 is connected to the actuating coil of motor circuit relay 28 and thence throughcar storage battery 50.

The positive side of storage battery 50 is connected to fixed contact 29 of the motor circuit relay, armature 39 of which is connected to one side of motor 14, the other side of the motor being grounded. The values of resistances 4d and 41 are so chosen that a delay bias of about 18 volts is impressed between the cathode 210 control electrode 21g,, and anode 2151 The negative side of the B supply is grounded, as usual.

It is noted that the left-hand half of tube 21 will now operate as a diode, but will not pass current until the magnitude of the incoming signal is sufiicient to overcome the effect of the delay bias. When there is insufficient signal to overcome the delay bias, control elecasaaasi trocle Zig will tend to go s to cathode 21o but flow of grid current is substantially prevented by resistor 23. The use of self-biasii1g resistor 24 reduces the increase of space current to anode 21o when the plate voltage rises, and this permits the use or" a low current winding in relay 25.

At the same time, the connection of the heater and the heater end of resistance 22 to +A and the connection of control electrode ii lg through resistances 23 and 22' to the same point, gives an increase of current for low values of the A voltage over what would otherwise be obtainable. By proper choice of these values, the constant plate current for high A voltage is maintained substantially constant, but What is more important, the plate current at low values of the A voltage is increased considerably, so that there is no danger of relay armature 27 opening or failing to close in the absence of a signal because of low battery voltage, and thus producing spurious stoppage of the tuner motor when no signal is being received, or failure to scan on closure of the manual switch to start scanning.

When a signal of sufiicient strength to override the delay bias is received, it is rectified between cathode 210 and electrodes Zig and 2111,, producing a negative potential which is impressed through resistance 23 on control electrode Zlg thereby reducing the plate current flowing through the actuating coil of relay 25 to such a point that armature 27 opens, thereby opening energizing coil of motor relay 28, permitting its armature 30 to move away from contact 29, opening the motor circuit, at which time the receiver is tuned to the incoming signal. The receiver will remain tuned to the incoming signal until the operator starts the tuning motor ,again, which may be done by closure of manual switch 51 parallel with motor relay contacts 29 and 30.

In case the positive side of car battery 59 is grounded, which may sometimes be the case (usually it is the negative terminal which is grounded), the negative side of car battery 50 will be connected to the common point of the heater leads, as in Fig. 2, the opposite ends of the heater leads may be grounded, and the lower end of resistor 22 may be grounded. Otherwise, the connections will be the same as in Fig. l, and, of course, the B voltage is derived from the A battery.

Still another possible modification is shown in Fig. 3, in which control electrode 21g; is now connected through resistance 33 to +B. This, as will be seen, provides a path to ground from +13 through resistance 33, ressitance 23, and resistance 22, in series. In this case it is desirable to make the value of resistance 33 high with respect to the sum of resistances 22 and 23.

Although some improvement is obtained by the use of the circuit of Fig. 3 as compared to conventional circuits, this circuit in general is not as effective as those of Fig. 1 and Fig. 2.

By way of example, and not in limitation, the following values are given for circuits which have been found to give good results:

i htly positive'with respect Ohms 7 Resistance 22 470,000 Resistance 23 470,000 Resistance 24- 550 Resistance 40 25,000 Resistance 41 150,000

When my invention is not employed, I have found that for an A battery voltage of 5 volts, the B voltage is Ais 5 voltsythe relay current is 6 ma., and when A is n "8-volts, the relay current is 13.6. In the'forrner case,

the range of current for fluctuation of A voltage from 5 volts to 8 volts is 8.8 ma, while when my invention is used, the fluctuation is 7.6 ma., a difierence of 1.2 ma. More significantly, it is seen that the current at low A voltage has been increased by 1.3 ma., while the current at high A voltage has been increased only 0.1 ma. Thus, it will be seen that the low A voltage current has been increased 27.6% while the high A voltage current has been increased only 0.74%.

fin the specification I have explained the principles of my invention and the best mode in which I have contemplated applying those principles, so as to distinguish my invention from other inventions; and I have particularly pointed out and distinctly claimed the part, improvement, or combination which I claim as my invention or discovery.

While I have shown and described certain preferred embodiments of my invention, it will be understood that modifications and changes may be made without departing from the spirit and scope thereof, as will be clear to those skilled in the art.

What I claim is:

1. In a control circuit for effecting a control function in response to an alternating current signal, the combination of means including a low-voltage battery for energizing said control circuit, a control tube having an anode, cathode, and control electrode, a relay having an energizing coil connected in the anode-cathode circuit of said tube, means for deriving from said battery a B voltage for energizing said coil and said anode-cathode circuit, rectifier means connected to be supplied with said alternating current signal to derive from said signal when it exceeds a predetermined amplitude a unidirectional voltage of negative polarity, means for applying a delay bias of said predetermined amplitude to said rectifier, means for applying a self bias to said control tube opposing increase of plate current with increased 'plate voltage, means for applying the negative voltage developed by said rectifier to said control electrode with respect to said cathode, and means for connecting said battery to said rectifier and to said control tube for causing an increase in the plate current of said control tube for a decrease in the value of the voltage of said battery.

2. In a signal-seeking receiver, in combination, a radio receiver, means including a low-voltage battery for energizing said receiver, a control tube having an anode, cathode, and control electrode, a relay having an energizing coil connected in the anode-cathode circuit of said tube, means for deriving from said battery a B voltage for energizing said coil and said anode-cathode circuit, rectifier means connected to said receiver to derive from received signals exceeding a predetermined amplitude a unidirectional voltage of negative polarity, means for applying a delay bias of said predetermined amplitude to said rectifier, means for applying a self bias to said control tube opposing increase of plate current with increased plate voltage, means for applying the negative voltage developed by said rectifier to said control electrode with respect to said cathode, and means forconnecting said battery to said rectifier and to said control tube for causing an increase in the plate current of said control tube for a decrease in the value of the voltage of said battery.

3. The combination claimed in claim 2, in which the negative terminal of said low voltage battery is grounded, and said last-mentioned means includes a connection between the positive terminal of said battery and the anode of said rectifier.

4. Ina signal seeking receiver adapted to be energized from a source of voltage, the combination of a control means responsive to an input voltage for efiecting a control function, means for energizing said control. means from said source, unidirectional impedance means coupled to said receiver for deriving a first unidirectional voltage, coupling means for coupling said unidirectional impedance means to the input of said control means, means for developing a second unidirectional voltage having a polarity opposite to that of said first unidirectional voltage and having a magnitude dependent upon the magnitude of the voltage of said source, means for connecting said last-named means to said impedance means so that said second unidirectional voltage provides a delay bias for said impedance means, means for developing a second bias voltage from said source and connecting it to said unidirectional impedance means in opposition to said delay bias voltage whereby the operating characteristics of said control means are maintained relatively constant irrespective of variations in the voltage of said source.

5. In a signal-seeking receiver in combination, a radio receiver, means including a low-voltage battery for energizing said receiver, a control tube having an anode, cathode, and control electrode, a relay having an energizing coil connected in the anode-cathode circuit of said tube, means energized by said battery for providing a B voltage for energizing said anode-cathode circuit, rectifier means coupled to said receiver'to derive from received signals exceeding a predetermined amplitude a unidirectional voltage of negative polarity, means for applying a delay bias of said predetermined amplitude to said rectifier, means for applying a self-bias to said control tube opposing increase of plate current thereof with increased plate voltage, means for applying the negative voltage developed by said rectifier to said control tube as a negative bias to reduce the plate current thereof with increasing amplitudes of said negative voltage, a connection from the positive terminal of said battery to ground, and a connection from the negative terminal of said battery to the cathode of said control tube, said connection including a resistance.

6. In a signal-seeking receiver in combination, a radio receiver, means including a low-voltage battery for energizing said receiver, a control tube having an anode, cathode, and control electrode, a relay having an energizing coil connected in the anode-cathode circuit of said tube, means energized by said battery for providing a B voltage for energizing said anode-cathode circuit, rectifier means coupled to said receiver to derive from received signals exceeding a predetermined amplitude a unidirectional voltage of negative polarity, means for applying a delay bias of said predetermined amplitude to said rectifier, means for applying a self bias to said control tube opposing increase of plate current thereof withincreased plate voltage, means for applying the negative voltage developed by said rectifier to said control tube as a bias to reduce the plate current thereof, a connection from the negative terminal of said battery to ground, and a connection from the positive terminal of said battery to the control electrode of said control tube, said connection including series resistance of sufficient magnitude to prevent the flow of substantial grid current.

7. In a signal-seeking receiver in combination, a receiver, means including a low-voltage battery for energizing said receiver, a control tube having an anode, cathode, and control electrode, a relay having an energizing coil connected in the anode-cathode circuit of said tube, means energized by said battery for providing a B voltage for energizing said anode-cathode circuit, rectifier means coupled to said receiver to derive from received signals exceeding a predetermined amplitude a unidirectional voltage of negative polarity, means for applying a delay bias of said predetermined amplitude to said rectifier, means for applying a self bias to said control tube opposing increase of plate current thereof with increased plate voltage, means for applying the negative voltage developed by said rectifier to said control electrode with respect to said cathode, a connection from the negative terminal of said battery to ground, a connection from the B voltage for energizing said anode-cathode circuit, rectifier means coupled to said receiver to derive from received signals exceeding a predetermined amplitude a unidirectional voltage of negative polarity, means for applying a delay bias of said predetermined amplitude to said rectifier, means for applying a self bias to said control tube opposing increase of plate current thereof with increased plate voltage, means for applying the negative voltage developed by said rectifier to said control electrode with respect to said cathode, a connection from the negative terminal of said battery to ground, a connection from the control electrode of said control tube to the positive terminal of said battery, said connection including in series a resistance connected in parallel with said rectifier.

9. In a signal-seeking receiver in combination, a radio receiver, means including a low-voltage battery for energizing said receiver, a control tube having an anode, cathode, and control electrode, a relay having an energizing coil connected in the anode-cathode circuit of said tube, means energized by said battery for providing a B voltage for energizing said anode-cathode circuit, rectifier means coupled to said receiver to derive from received signals exceeding a predetermined amplitude a unidirectional voltage of negative polarity, means for applying a delay bias of said predetermined amplitude to said rectifier, means for applying a self bias to said control tube opposing increase of plate current thereof with increased plate voltage, means for applying the negative voltage developed by said rectifier to said control tube as a bias to reduce the plate current thereof, a connection from the positive terminal of said battery to ground, and a connection from the negative terminal of said battery to the cathode of said control tube through a resistance.

10. In a signal-seeking receiver in combination, a receiver, means including a low-voltage battery for energizing said receiver, a control tube having an anode, cathode, and control electrode, a relay having an energizing coil connected in the anode-cathode circuit of said tube, means energized by said battery for providing a B voltage for energizing said anode-cathode circuit, rectifier means coupled to said receiver to derive from received signals exceeding a predetermined amplitude a unidirectional voltage of negative polarity, means for applying a delay bias of said predetermined amplitude to said rectifier, means for applying a self bias to said control tube opposing increase of plate current thereof with increased plate voltage, means for applying the negative voltage developed by said rectifier to said control electrode with respect to said cathode as a bias, a source of unidirectional plate voltage, and a connection from the positive terminal of said source to the control electrode of said control tube, said connection including a dropping resistor.

11. In a signal-seeking receiver in combination, a receiver, means including a low-voltage battery for energizing said receiver, a control tube having an anode, cathode, and control electrode, means energized by said battery for providing a B voltage for energizing said anode-cathode circuit, a relay having an energizing coil connected in the anode-cathode circuit of said tube, rectifier means coupled to said receiver to derive from received signals exceeding a predetermined amplitude a unidirectional voltage of negative polarity, means for applying a delay bias of said predetermined amplitude to said rectifier, means for applying a self bias to said control :tube opposing increase of plate current thereof with increasedplate voltage, means for applying the negative voltage developed by said rectifier to said control electrode with respect to said cathode, a source of unidirectional plate voltage, a connection from the positive terminal of said source to ground through a path termediate point of said resistance to the control electrode of said control tube.

References Cited in the file of this patent UNITED STATES PATENTS V Koch Jan. 17, 1939 V Smith Apr. 4, 1944 :Jadraque et al :Aug. 7, 1945 Clay Mar. 26, 1946 Levy Jan. 27, 1948 Hastings July 12, 1949 Parnsworth "Sept. 6, 1949 Weiss' Feb. 24, 1953 

